package cn.jx.asc.common.filter;


import cn.hutool.json.JSONUtil;
import cn.jx.asc.common.jwt.JwtToken;
import cn.jx.asc.common.response.Result;
import cn.jx.asc.common.response.ResultUtils;
import cn.jx.asc.common.enums.ResultStatus;
import lombok.extern.slf4j.Slf4j;
import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;


/**
 * @author lhg
 */

@Slf4j
public class JwtFilter extends BasicHttpAuthenticationFilter {
    /**
     * 判断用户是否想要登入。
     * true:是要登录
     * 检测header里面是否包含Authorization字段即可
     */
    @Override
    protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
        HttpServletRequest req = (HttpServletRequest) request;
        String authorization = req.getHeader("Authorization");
        return authorization != null;
    }

    /**
     *
     */
    @Override
    protected boolean executeLogin(ServletRequest request, ServletResponse response)  throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        String authorization = httpServletRequest.getHeader("Authorization");
        JwtToken token = new JwtToken(authorization);
        // 提交给realm进行登入，如果错误他会抛出异常并捕获
        try{
            getSubject(request, response).login(token);
        }catch (Exception e){
            log.error("认证失败: " + e.getMessage());
            responseErrorMag(response, e.getMessage());
            return false;
        }
        // 如果没有抛出异常则代表认证成功，返回true
        return true;

    }

    /**
     * 这里我们详细说明下为什么最终返回的都是true，即允许访问
     * 例如我们提供一个地址 GET /article
     * 登入用户和游客看到的内容是不同的
     * 如果在这里返回了false，请求会被直接拦截，用户看不到任何东西
     * 所以我们在这里返回true，Controller中可以通过 subject.isAuthenticated() 来判断用户是否登入
     * 如果有些资源只有登入用户才能访问，我们只需要在方法上面加上 @RequiresAuthentication 注解即可
     * 但是这样做有一个缺点，就是不能够对GET,POST等请求进行分别过滤鉴权(因为我们重写了官方的方法)，但实际上对应用影响不大
     */
    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        //1. 首先检查请求头中是否有 token 访问令牌
        //  有: 将令牌交给 Realm 进行校验
        //  没有: 直接不允许访问, 因为设置了 login 和 register 不走这个过滤器
        if(isLoginAttempt(request, response)){
            try{
                this.executeLogin(request, response);
                return true;
            }catch (Exception e){
                responseErrorMag(response, e.getMessage());
                return false;
            }
        }
        responseErrorMag(response, "您如果想要执行此操作,请提供正确的凭证信息!");
        log.warn("用户尝试使用错误的凭证信息访问系统");
        return false;
    }

    /**
     * 对跨域提供支持
     */
    @Override
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
        httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
        httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
        // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
        if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
            httpServletResponse.setStatus(HttpStatus.OK.value());
            return false;
        }
        return super.preHandle(request, response);
    }


    /**
     * 重写 onAccessDenied 方法，避免父类中调用再次executeLogin
     * @param request ServletRequest
     * @param response ServletResponse
     * @return boolean
     */
    @Override
    protected boolean onAccessDenied(ServletRequest request, ServletResponse response) {
        log.warn("调用onAccessDenied拒绝访问");
        this.sendChallenge(request, response);
        return false;

    }

    /**
     * 返回json格式对象
     * @param response ServletResponse
     * @param msg String
     */
    private void responseErrorMag(ServletResponse response, String msg) {
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setStatus(HttpStatus.UNAUTHORIZED.value());
        httpServletResponse.setCharacterEncoding("UTF-8");
        httpServletResponse.setContentType("application/json; charset=utf-8");

        try (PrintWriter out = new PrintWriter(response.getOutputStream())) {
           Result result = ResultUtils.resultWithoutData(ResultStatus.FAILED, msg);
           out.append(JSONUtil.toJsonStr(result));
        } catch (IOException e) {
            log.error("返回Response信息出现IOException异常: {}", e.getMessage());
        }

    }
}


